Vibratory system



April 28, 1925. 1,535,527

' H. C. HARRISON VIBRATORY SYSTEM Filed Jan. 1923 PHASE SH/FYERflvvemar: Haw/y Ch r/son by 456 W W.

Patented Apr. 28, 1 925.

UNITED STATES PATENT OFFICE.

HENRY C. HARRISON, OF PORT WASHINGTON, NEW YORK, ASSIGNOR TO WESTERNELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEWYORK.

'VIBRATORY SYSTEM.

Application filed January 3, 1923. Serial No. 610,528.

To all whom it may concern.

Be it known that I, I'IENRY C. HARRISON, a citizen of the United States,residing at Port Washington, in the county of Nassau, I State of NewYork, have invented certain new and useful Improvements in VibratorySystems, of which the following is a full, clear, concise, and exactdescription.

This invention relates to vibratory systerns, and more. particularlyrelates to inechanical vibratory systems which are electrically driven.k One object of this invention is to reduce distortion in a vibratorysystem.

Another object is to provide means and methods for damping themechanical vibration of a moving system.

As is well-known in theart, mechanical vibratory systems, such as atelephone receiver diaphragm, or the like, frequently possess resonancecharacteristics and tend to overemphasize certain frequencies or handsoffrequencies, thereby failing to give faithful reproductions of theimpressed forces. This resonance is not a serious objection in manycases, but occasions do arise when it is found desirable to. providesome means for overcoming the resonance effect by damping, for example.Y Y 80 In accordance with one form of this invention, a mechanicalvibratory system is given a substantially constant response over a widefrequency range by causing a part-of the vibratory system to act as anarmature 85 for an electro-magnet which has a magnetizing windingconnected to the input terminals of a vacuum tube amplifier. The outputterminals of the amplifier are connected to an auxiliary winding on theelectromagnet in such a manner that the alternating currents in theauxiliary Winding neutralize the reactive component of themagneto-motive forces of the alternating currents in the first winding.That is, the reactive component of the impedance opposing the flow ofeddy currents in the first winding due to the voltages generated bythevibration of the armatureis neutralized so that there will be noreactive effect due to the storage of power in the system, thus giving apure resistance damping. This arrangement for producing damping by theneutralization of the reactive component of the impedance of themagnetizihg winding is of wide application and capable of use in varioustypes of mechanically vibrating systems.

Referring to the drawings, Fig. 1 illustrates this invention adapted todampen the vibrations of a telephone receiver diaphragm; Fig. 2 showshow this invention may be applied to dampen the vibrations of thearmature of an electrical phonograph recorder; and Fig. 3 illustartesone type of phase shifter which may be employed with this invention.

Referring to Fig. 1, an electromagnetic receiver is disclosed thereincomprising a diaphragm 7, coupled by members 8 and 9 to an armature 10,which is pivoted between the pole pieces of a permanent magnet 11.Surrounding the armature 10 are two coils 12 and 13, which are connectedto a suitable incoming line 14, such as a telephone line. Alternatingcurrents present in line 14, will in a manner well-known in the art,cause armatu're 10 to vibrate, thereby causing, the vibration of thediaphragm 7, so that sound waves are produced by the diaphragm corresponding to the currents present in line 14. Such an arrangement,however, frequently tends to over-em hasize certain frequencies or handsof requencies, due to resonance in the diaphragm.

Inaccordance with this invention this over-emphasizing of certainfrequencies by the telephone diaphragm may be substantially avoided andthe vibrating system given a substantially constant'response over a Widefrequency range by having the mechanical system damped in a manner nowto be described.

A small electromagnet 15 is placed adj acent the magnetic member 9,whereby the vibration of the armature 10 will cause member 9 to be movedtowards and away from the pole pieces of electromagnet 15 in accordancewith the signaling or other alternating currents present in line 14. The

magnetizing winding 16 for electromagnet 15 has its terminals connectedin series with a source of voltage 17, and a low resistance 18, one sideof resistance 18 being connected through a condenser 19 to the controlelectrode, and the other side of resistance 18 to the cathode of avacuum tube amplifier 10. The output terminals of amplifier 20 are be soadjusted that the currents in coil 22 substantially neutralize thereactive component of the magneto-motive forces present in the magnet 15due to the currents in coil 16. With such an arrangement, the eddycurrents will be in phase with the voltage induced by the armaturevibrations that is in phase with the velocity of the armature and sowill give a pure resistance damping. The amount of damping, of course,will be dependent, to some extent upon the size of electromagnet 15 andthe number of turns and resistance of winding 16, since the greater thenumber of turns in winding 16 and the lower the resistance the greaterwill be the damping.

Electromagnet 15 willftherefore, dampen the vibration of armature 9 andwill substantially eliminate the resonance characteristics of thediaphragm 7 whereby the telephone receiver will have a substantiallyconstant response over a wide range of frequency for the currentspresent in line 14.

The phase shifter 21 may be of a suitable type either of a singlesection or' a plurality of sections, depending upon the phase shiftdesired, and also upon the range of frequencies for which it is desiredto produce a constant displacement in phase. Fig. 3 for example shows aphase shifter comprising series inductances 40, 41 and 42 and shuntcapacities 43 and 44.

Fig. 2 is similar to Fig. 1, except that an electromagnet 15 has itspole pieces close to the pivoted armature 25 of a permanent ma net 26 ofan electrical phonograph recorde'r. The lower end of armature 25 isshown to be terminated in a suitable needle 27, which may be employedfor producing a sound record 28 corresponding to the electrical currentspresent in line 29, which is connected in circuit with the two coils 30and 31 surrounding the armature. Winding 16, amplifier 20, battery 21and auxiliary winding 22 may therefore be employed in the same manner asin Fig. 1 whereby resonance characteristics in the vibration of armature25 may be substantially elimimated by the damping effect due to the presence of the electromagnet 15 and the presence of the special equipmentconnected thereto.

The above specific forms of this invention are merely illustrative ofthe wide field in which this invention may be employed,-and it is to beunderstood that this invention may be employed in forms widely differentfrom those just described without departing in anywise from the spiritof this invention as defined in the appended claims.

The invention claimed is:

1. A. vibrating system subjected to a force for causing the system tovibrate, a magnetic member subjected to flux variations when said systemvibrates a coil surrounding ,said member, means for supplying directcurrent to said coil, an auxiliary coil'on said member, and means forproducing in said aux-- iliary coil alternating currents whichsubstantially neutralize the reactive component of the magneto motiveforces of the alternating currents in said first coil produced by thevibration of said system.

2. A vibrating system subjected to a force for causing the system tovibrate, a magnetic member subjected to flux variations when said systemvibrates, a coil surrounding said member, and means responsive to saidflux variations for substantially neutralizing the reactive component ofthe magneto motive forces of the alternating currents in said coilproduced in said coil by the vibrations of said system.

3. A vibrating system subjected to a force for causing the system tovibrate, a magnetic member subjected to fiux variations when said systemvibrates, a coil surrounding said member, amplifying means having inputand output terminals, an auxiliary coil on said member, connectionsbetween said input terminals and said first coil, and connectionsbetween said output terminals and said auxiliary coil, said connectionsbeing arranged to produce in said auxiliary coil alternating currentsproducing magneto motive forces opposing the alternating currentsproduced in said first winding by the vibration of said system.

4. An electromagnet having an armature, a plurality of windings on saidmagnet, a vacuum tube having input and output terminals, connectionsfrom said input -terminals to one of said windings, connections fromsaid output terminals to a second of said windings, and phase shiftingmeans in said output circuit.

5. An electromagnet having an armature, a plurality of windings on saidmagnet, a vacuum tube having input and output terminals, connectionsfrom said input terminals to one of said windings, means for impressingan audible frequency on said winding. connections from said outputterminals to a second of said windings, and means for preventing saidtube from singing at' an audible frequency.

' 6. In combination, a magnet having a pivoted armature, a windingsurrounding said armature, an electric circuit connected to said windingto cause said armature to vibrate in accordance with currents present insaid circuit, an auxiliary electromagnet ubjected to flux variationswhen said armature vibrates, a magnetizing Winding for saidelectromagnet, a vacuum tube amplifier, means for supplying directcurrent to said winding, means for impressing on said amplifierpotential variations corresponding to the potential variations producedin said winding by the said flux variations, and means for causing thepotential variations amplified by said amplifier to produce magnetomotive forces which substantially neutralize the reactive component ofthe alternating currents in said winding. I

" 7. In combination, a magnet having a pivoted armature, a windingsurrounding said armature, an electric circuit connected to said windingto cause the vibration of said armature in accordance with alternatingcurrent variations in said circuit, and means for damping the vibrationof said armature, said means comprising an an}. iliary electromagnetsubjected to flux variations when said armature vibrates, a magnetizingWinding on said electromagnet, means for supplying direct current tosaid winding, an auxiliary winding on said electromagnet, a vacuum tubeamplifier having 7 its input terminals connected to said mags netizingwinding and its output terminals connected to said auxiliary winding,and means for causing the reactive component of the alternating currentsproduced in said magnetizing winding by said flux variations to besubstantially neutralized by magnetomotive forces Winding.

In witness whereof, I hereunto subscribe my name this 26th day ofDecember, A. D. 1922.

produced by said auxiliary HENRY "c. 'IIARRISON.

